Thomas B. Hofstetter is a lecturer in environmental organic chemistry in the department of environmental sciences and a senior scientist at the Institute of Biogeochemistry and Pollutant Dynamics at the Swiss Federal Institute of Technology (ETH) Zurich. Before moving to ETH Zurich, he was a guest investigator at Woods Hole OceanographicInstitution(WHOI) and a senior researcher at the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and at the Institute of Chemical and Bioengineering of ETH Zurich. His research focuses on the pathways and mechanisms of organic contaminant formation and degradation. He also uses contaminants as reactive probe molecules to investigate the biogeochemical cycling of iron and how its redox activity in oxides and clay minerals is affected by the activity of microbes. Among his earlier works on stable isotopes is a study of the combined effects of carbon and chlorine (at the time, rarely used) isotopes during transformations of chlorohydrocarbons, which was honored by ES&T as one of the best science papers of 2007. He has pioneered the use of nitrogen isotopes in organic contaminants to investigate the mechanisms of surface catalysis, enzymatic reactions, and photochemical processes. His most recent applications apply stable isotopes to elucidate the formation pathways of drinking-water byproducts. A co-organizer (together with Stefano Bernasconi, Roland Werner, and Rene´ Schwarzenbach) of an interdisciplinary international workshop on stable isotopes held in Switzerland in 2007 (which sparked the idea for this focus issue), he is very interested in the scientific exchange among practitioners of the various disciplines relying on isotopic tools, from (bio)chemistry to earth sciences.
Stefano M. Bernasconi is a senior scientist and lecturer in the department of earth sciences at ETH Zurich, where he heads the stable isotope and organic geochemistry laboratories. His main research focuses on the study of natural biogeochemical cycles at different temporal and spatial scales. He has worked extensively on carbon and nitrogen cycling in lakes as a way to understand the factors controlling the carbon and nitrogen isotope composition of lacustrine organic matter. His research also focuses on the factors influencing sulfur isotope fractionation during 7728 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / November 1, 2008
microbial sulfate reduction, through studies of interstitial waters from marine sediments, groundwaters, hydrothermal systems, the rocks underlying such marine hydrothermal systems, and bacterial cultures. These studies have led to the formulation of a new model to explain sulfur and oxygen isotope variations in sulfate. Other areas of research interest are the application of isotopes and organic geochemistry to reconstruct changes in climate and the carbon cycle through geologic time, and examination of the processes controlling the preservation of organic carbon in sediments. In this context he is further developing isotopic methods to determine paleotemperatures from carbonates on the basis of multiply substituted isotopic molecules. More recently, he has expanded his interests to terrestrial biogeochemistry and is leading a large interdisciplinary project on weathering, soil formation, and ecosystem evolution. This project is developing a new multidisciplinary approach and novel isotope techniques, such as compound-specific radiocarbon measurements, to elucidate the processes controlling rates of weathering and of soil formation.
Rene´ P. Schwarzenbach is a full professor of environmental chemistry and the head of the department of environmental sciences at ETH Zurich. He is also the president of Division IV of the Swiss National Science Foundation. He earned his Ph.D. in chemistry at ETH Zurich in 1973. After spending two postdoctoral years at WHOI, he accepted a position in 1977 at Eawag, where he later served on the Board of Directors until April 2005. In 1989 he was appointed full professor at ETH Zurich. In 1992, he was awarded the Ko¨rber Prize for Science, with four colleagues from Germany, France, and Switzerland. In 2000, he was selected to be an original member of the ISI Highly Cited Researchers Database, in 2001 he won the Society of Environmental Toxicology and Chemistry Environmental Education Award, and in 2006 he became the first person working outside of the U.S. to receive the American Chemical Society Award for Creative Advances in Environmental Science and Technology. He is a researcher, teacher, and consultant, and his group’s activities focus primarily on the distribution, fate, and effects of organic pollutants in the natural environment. Their research addresses fundamental chemical as well as multidisciplinary system-oriented aspects of these pollutants. In his teaching, he aims to build bridges between the molecular world and macroscopic systems. His textbook Environmental Organic Chemistry, which he coauthored with two colleagues from the Massachusetts Institute of Technology and ETH Zurich, won the Chemistry Book of the Year Award of the Association of American Publishers in 1994 and has become the standard text in the field of environmental organic chemistry. 10.1021/es8027742
2008 American Chemical Society
Published on Web 10/30/2008
Ruben Kretzschmar is a full professor of soil chemistry in the department of environmental sciences at ETH Zurich. Currently, he is also a Cox Visiting Professor at the department of environmental earth system science in the School of Earth Sciences at Stanford University. He serves as chair of Division 2 in the International Union of Soil Sciences. After studying agricultural sciences at the University of Hohenheim (Germany), he earned his Ph.D. in soil science from North Carolina State University. During his graduate studies, he specialized in plant nutrition, environmental soil chemistry, and soil mineralogy. His early research investigated the influence of solution and surface chemistry on the
stability, transport, and deposition of colloidal particles (including nanoparticles) in natural porous media. Later research focused on trace metal sorption to minerals and natural organic matter, modeling competitive sorption and reactive transport of trace metals, long-term changes in trace metal speciation in soils by synchrotron X-ray spectroscopy, and the dissolution of iron oxide minerals in the presence of siderophores and organic acids. Most recently, his group has explored the biogeochemical processes that control the speciation and cycling of trace elements in periodically flooded soils, such as contaminated river floodplains and paddy soils. With isotope geochemists at ETH Zurich, his group is also investigating isotope fractionation effects of elements such as iron, calcium, lithium, and mercury in the terrestrial environment. Kretzschmar became an associate editor of ES&T in September 2007 and is on the editorial boards of two other journals. ES8027742
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